[31.04] Resolving the Enigmatic Northern Arm Sources in the Central Parsec

AAS 201st Meeting, January, 2003
Session 31. The Galactic Center and Its Environs
Oral, Monday, January 6, 2003, 2:00-3:30pm, 6AB

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[31.04D] Resolving the Enigmatic Northern Arm Sources in the Central Parsec

A. Tanner (UCLA)

Diffraction limited 2-25 micron images of the central parsec of the Galactic Center obtained with the Keck telescope have spatially resolved the cool Northern Arm sources IRS 1W, 5, 21 and 2; enigmatic objects that have eluded classification. We have used their azimuthally averaged radial profiles to estimate Gaussian convolved near- and mid-infrared sizes of ~1500 AU and ~3000 AU, respectively. This, along with models of their SEDs, reveal they are centrally heated stellar sources surrounded by geometrically thin dust distributions. Our near-infrared Keck/NIRC/NIRC2 images as well as Gemini AO images of IRS 8 reveal asymmetric dust structures around these sources indicative of bowshocks. Comparisons of the observed near-infrared sizes to the expected bowshock standoff distances, derived using the observed proper motion of the near-IR source and the modeled proper motion of the Northern Arm material, suggest that these sources must have winds of at least 1500 km/s; thus they are windy, massive stars embedded within the infalling Northern Arm. Despite the lack of observed photospheric emission, the bowshock morphology of these sources allows us to identify them as late type Wolf-Rayet (WCL) stars similar to the distinct central parsec population of nine such stars previously identified through broad He I emission lines by Paumard et al. (2001). The large near-IR sizes distinguish the Northern Arm sources from other sources with similar large K-L colors and/or mid-infrared fluxes found both in the central parsec (IRS 3, 7, 29N and 6E) and nearby Quintuplet cluster. However, the total population of such massive, evolved stars in both 3-6 Myr old clusters is similar despite the close proximity of the central parsec cluster to the supermassive black hole, Sgr A*.

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The author(s) of this abstract have provided an email address for comments about the abstract: tanner@astro.ucla.edu

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